#pragma GCC optimize ("O2")
#pragma GCC target ("avx2")
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i, n) for(int i = 0; i < (n); i++)
#define rep1(i, n) for(int i = 1; i <= (n); i++)
#define co(x) cout << (x) << "\n"
#define cosp(x) cout << (x) << " "
#define ce(x) cerr << (x) << "\n"
#define cesp(x) cerr << (x) << " "
#define pb push_back
#define mp make_pair
#define chmin(x, y) x = min(x, y)
#define chmax(x, y) x = max(x, y)
#define Would
#define you
#define please

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);


	int N;
	cin >> N;
	int A[100000], B[100000];
	rep(i, N) cin >> A[i];
	rep(i, N) cin >> B[i];

	if (N == 2) {
		if (A[0] + A[1] == B[0] + B[1]) {
			co(abs(A[0] - B[0]));
		}
		else {
			co(-1);
		}
		return 0;
	}

	ll sa = 0;

	rep(i, N) sa += A[i] - B[i];
	if (sa % (N - 2)) {
		co(-1);
		return 0;
	}
	
	ll wari = sa / (N - 2);
	ll kaisuu = 0;
	int OK = 1;
	rep(i, N) {
		ll a = A[i] - wari;
		if (a > B[i]) OK = 0;
		if ((B[i] - a) % 2) OK = 0;
		kaisuu += (B[i] - a) / 2;
	}

	if (!OK || kaisuu > wari) co(-1);
	else co(wari);

	Would you please return 0;
}